Singer Professional 2010 and feed dogs?

I put the feed dogs down to do stippling with the embroidery foot and the feed dogs pop back up on their own. I do not touch the handle, I just keep sewing as normal, with the fool lever down and just keep going. But after two days of it being ok, now they pop back up on their own. Why is this happening? The lever slides itself back to the other side.
Also, the embroidery foot that came with it, made a huge gauge in the metal pin that holds the needle tightening screw, it rubbed on it and now there is a groove. I am using a foot that came with my singer futura and it works better, but why? But the feed dog issue is driving me nuts!

Nancy
March 2010